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Commit 56abaa09 authored by Frederick Mayle's avatar Frederick Mayle Committed by Christopher Ferris
Browse files

debuggerd: simplify output handling 

Just noticed some opportunities while skimming.

Test: adb shell debuggerd $(adb shell pidof com.android.systemui)
Test: All unit tests pass (both 32 bit and 64 bit).
Test: Ran unit tests in a loop hundreds of times.
Change-Id: I428d0cf599ed603a21944b084b95594db893cbd5
parent 6e80656b

debuggerd/client/debuggerd_client.cpp

+7 −0
Original line number Diff line number Diff line
@@ -276,6 +276,13 @@ bool debuggerd_trigger_dump(pid_t tid, DebuggerdDumpType dump_type, unsigned int 
      return false;

    }



    // WARNING: It's not possible to replace the below with a splice call.

    // Due to the way debuggerd does many small writes across the pipe,

    // this would cause splice to copy a page for each write. The second

    // pipe fills up based on the number of pages being copied, even

    // though there is not much data being transferred per page. When

    // the second pipe is full, everything stops since there is nothing

    // reading the second pipe to clear it.

    char buf[1024];

    rc = TEMP_FAILURE_RETRY(read(pipe_read.get(), buf, sizeof(buf)));

    if (rc == 0) {

debuggerd/debuggerd.cpp

+4 −24
Original line number Diff line number Diff line
@@ -41,22 +41,6 @@ static void usage(int exit_code) { 
  _exit(exit_code);

}



static std::thread spawn_redirect_thread(unique_fd fd) {

  return std::thread([fd{ std::move(fd) }]() {

    while (true) {

      char buf[BUFSIZ];

      ssize_t rc = TEMP_FAILURE_RETRY(read(fd.get(), buf, sizeof(buf)));

      if (rc <= 0) {

        return;

      }



      if (!android::base::WriteFully(STDOUT_FILENO, buf, rc)) {

        return;

      }

    }

  });

}



int main(int argc, char* argv[]) {

  if (argc <= 1) usage(0);

  if (argc > 3) usage(1);
@@ -107,14 +91,11 @@ int main(int argc, char* argv[]) { 
    }

  }



  unique_fd piperead, pipewrite;

  if (!Pipe(&piperead, &pipewrite)) {

    err(1, "failed to create pipe");

  unique_fd output_fd(fcntl(STDOUT_FILENO, F_DUPFD_CLOEXEC, 0));

  if (output_fd.get() == -1) {

    err(1, "failed to fcntl dup stdout");

  }



  std::thread redirect_thread = spawn_redirect_thread(std::move(piperead));

  if (!debuggerd_trigger_dump(proc_info.pid, dump_type, 0, std::move(pipewrite))) {

    redirect_thread.join();

  if (!debuggerd_trigger_dump(proc_info.pid, dump_type, 0, std::move(output_fd))) {

    if (pid == proc_info.pid) {

      errx(1, "failed to dump process %d", pid);

    } else {
@@ -122,6 +103,5 @@ int main(int argc, char* argv[]) { 
    }

  }



  redirect_thread.join();

  return 0;

}